1. Field of the Invention
The present invention generally relates to brake rotors for motor vehicles, and more particularly to brake rotors which are suitable for use on race cars.
2. Background Information
In automobile racing, as well as in other contexts relating to motor vehicles, there can be several critical factors which may influence the performance of the vehicle in question. One important factor is weight, in that an excessively heavy vehicle may not be able to perform effectively. This factor may, for example, have a decisive influence on the speed and fuel economy of the vehicle. Another important factor may be the ability for the vehicle to brake effectively. Particularly, the ability of the vehicle to stop quickly and efficiently, as well as the need to prevent excessive overheating of the brakes, can be tremendously important.
Conventionally, brake rotors have been formed of cast iron or steel, and often do not have a coating for serving as a thermal barrier.
A disadvantage often encountered with such rotors is excessive weight, both in terms of unsprung weight and rotating weight. Such excessive weight may often result in poor fuel economy, as well as an inhibited capability to accelerate. Typically, such a rotor may weigh approximately fifteen pounds, which would typically result in a total weight, for four brake rotors in a vehicle, of about sixty pounds. This has long been considered to be excessive for certain contexts, particularly for the context of race cars.
In conventional rotors, braking problems may also result from a coefficient of friction which may not be as high as desired for certain applications, such as in the context of race cars. In the case of conventional cast iron rotors, another disadvantage often encountered is the presence of voids or stresses in the casting.
It has been known that the weight of conventional rotors can be reduced by utilizing a lighter material, such as aluminum. If, for example, a lightweight rotor, which may include aluminum, is provided in a vehicle, such as a race car, the unsprung weight and rotating weight of the vehicle may be reduced by as much as forty-eight pounds, particularly if each rotor weighs only about three or four pounds.
It has also been known to coat the braking surfaces of a brake rotor with ceramic, in order to provide a higher coefficient of friction than would normally be encountered with a plain cast iron or steel rotor. To date, such ceramics have often included a variety of materials. However, problems relating to durability may be experienced in these contexts. Particularly, in many known applications, it has been found that the ceramic coating may have a tendency to develop cracks with increased use, especially if high braking temperatures are created at the surface of the ceramic coating.
U.S. Pat. No. 5,224,572 discloses the provision of a ceramic coating on each of the two braking surfaces of an aluminum rotor. As disclosed therein, a plurality of circumferentially spaced cooling apertures are arranged between the braking surfaces. The apertures extend radially, between the large central aperture of the rotor and the outer circumference of the rotor, and essentially act to vent away excessive heat. However, it has been found that this aluminum veined rotor is not necessarily provided with as significant a degree of thermal protection as may often be desired in certain contexts, such as in the context of a racing car. Further, it has also been found that this aluminum veined rotor does not necessarily provide as great a reduction in either unsprung weight or rotating weight as may otherwise be desired in certain contexts, such as in the context of a racing car.